Tungsten feature fill with nucleation inhibition

ABSTRACT

Described herein are methods of filling features with tungsten, and related systems and apparatus, involving inhibition of tungsten nucleation. In some embodiments, the methods involve selective inhibition along a feature profile. Methods of selectively inhibiting tungsten nucleation can include exposing the feature to a direct or remote plasma. In certain embodiments, the substrate can be biased during selective inhibition. Process parameters including bias power, exposure time, plasma power, process pressure and plasma chemistry can be used to tune the inhibition profile. The methods described herein can be used to fill vertical features, such as in tungsten vias, and horizontal features, such as vertical NAND (VNAND) wordlines. The methods may be used for both conformal fill and bottom-up/inside-out fill. Examples of applications include logic and memory contact fill, DRAM buried wordline fill, vertically integrated memory gate/wordline fill, and 3-D integration using through-silicon vias.

INCORPORATION BY REFERENCE

An Application Data Sheet is filed concurrently with this specificationas part of the present application. Each application that the presentapplication claims benefit of or priority to as identified in theconcurrently filed Application Data Sheet is incorporated by referenceherein in its entirety and for all purposes.

BACKGROUND

Deposition of tungsten-containing materials using chemical vapordeposition (CVD) techniques is an integral part of many semiconductorfabrication processes. These materials may be used for horizontalinterconnects, vias between adjacent metal layers, contacts betweenfirst metal layers and devices on the silicon substrate, and high aspectratio features. In a conventional deposition process, a substrate isheated to a predetermined process temperature in a deposition chamber,and a thin layer of tungsten-containing materials that serves as a seedor nucleation layer is deposited. Thereafter, the remainder of thetungsten-containing material (the bulk layer) is deposited on thenucleation layer. Conventionally, the tungsten-containing materials areformed by the reduction of tungsten hexafluoride (WF₆) with hydrogen(H₂). Tungsten-containing materials are deposited over an entire exposedsurface area of the substrate including features and a field region.

Depositing tungsten-containing materials into small and, especially,high aspect ratio features may cause formation of seams and voids insidethe filled features. Large seams may lead to high resistance,contamination, loss of filled materials, and otherwise degradeperformance of integrated circuits. For example, a seam may extend closeto the field region after filling process and then open duringchemical-mechanical planarization.

SUMMARY

One aspect described herein is a method involving providing a substrateincluding a feature having one or more feature openings and a featureinterior, selectively inhibiting tungsten nucleation in the feature suchthat there is a differential inhibition profile along a feature axis;and selectively depositing tungsten in the feature in accordance withthe differential inhibition profile. Methods of selectively inhibitingtungsten nucleation in the feature include exposing the feature to adirect plasma or a remote plasma. In certain embodiments, the substratecan be biased during selective inhibition. Process parameters includingbias power, exposure time, plasma power, process pressure and plasmachemistry can be used to tune the inhibition profile. According tovarious embodiments, the plasma can contain activated species thatinteract with a portion the feature surface to inhibit subsequenttungsten nucleation. Examples of activated species include nitrogen,hydrogen, oxygen, and carbon activated species. In some embodiments, theplasma is nitrogen and/or hydrogen-based.

In some embodiments, a tungsten layer is deposited in the feature priorto any selective inhibition of tungsten nucleation. In otherembodiments, selective inhibition is performed prior to any tungstendeposition in the feature. If deposited, a tungsten layer may bedeposited conformally, in some embodiments, for example by a pulsednucleation layer (PNL) or atomic layer deposition (ALD) process.Selective deposition of tungsten in the feature can be performed by achemical vapor deposition (CVD) process.

After selectively depositing tungsten in the feature, tungsten can bedeposited in the feature to complete feature fill. According to variousembodiments, this can involve non-selective deposition in the feature orone or more additional cycles of selective inhibition and selectivedeposition. In some embodiments, transitioning from selective tonon-selective deposition involve allowing a CVD process to continuewithout deposition of an intervening tungsten nucleation layer. In someembodiments, a tungsten nucleation layer can be deposited on theselectively deposited tungsten, e.g., by a PNL or ALD process, prior tonon-selective deposition in the feature.

According to various embodiments, selectively inhibiting tungstennucleation can involve treating a tungsten (W) surface, or a barrier orliner layer, such as a tungsten nitride (WN) or titanium nitride (TiN)layer. Selective inhibition can be performed with or withoutsimultaneous etching material in the feature. According to variousembodiments, at least a constriction in the feature is selectivelyinhibited.

Another aspect of the invention relates to a method include exposing afeature to an in-situ plasma to selectively inhibit a portion of thefeature. According to various embodiments, the plasma can benitrogen-based, hydrogen-based, oxygen-based, or hydrocarbon-based. Insome embodiments, the plasma can contain a mixture of two or more of anitrogen-containing, hydrogen-containing, oxygen-containing, orhydrocarbon-containing gas. For example, an unfilled or partially filledfeature may be exposed to a direct plasma to thereby selectively inhibittungsten nucleation of a portion of the feature such that there is adifferential inhibition profile in the feature. In some embodiments,after selectively inhibiting a portion of the feature, performing a CVDoperation to thereby selectively deposit tungsten in accordance with thedifferential inhibition profile.

Another aspect of the invention relates to single and multi-chamberapparatus configured for feature fill using selective inhibition. Insome embodiments, an apparatus includes one or more chambers configuredto support a substrate; an in situ plasma generator configured togenerate a plasma in one or more of the chambers; gas inlets configuredto direct gas into each of the one or more chambers; and a controllerhaving program instructions for generating a plasma such as anitrogen-based and/or hydrogen-based plasma while applying a bias powerto the substrate such that the substrate is exposed to the plasma, afterexposing the substrate to the plasma, inletting a tungsten-containingprecursor and a reducing agent to a chamber in which the substrate sitsto deposit tungsten.

These and other aspects are described further below.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-1G show examples of various structures that can be filledaccording to the processes described herein.

FIGS. 2-4 are process flow diagrams illustrating certain operations inmethods of filling features with tungsten.

FIGS. 5-7 are schematic diagrams showing features at various stages offeature fill.

FIGS. 8-9B are schematic diagrams showing examples of apparatus suitablefor practicing the methods described herein.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Thepresent invention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail to not unnecessarily obscure the present invention.While the invention will be described in conjunction with the specificembodiments, it will be understood that it is not intended to limit theinvention to the embodiments.

Described herein are methods of filling features with tungsten andrelated systems and apparatus. Examples of application include logic andmemory contact fill, DRAM buried wordline fill, vertically integratedmemory gate/wordline fill, and 3-D integration with through-silicon vias(TSVs). The methods described herein can be used to fill verticalfeatures, such as in tungsten vias, and horizontal features, such asvertical NAND (VNAND) wordlines. The methods may be used for conformaland bottom-up or inside-out fill.

According to various embodiments, the features can be characterized byone or more of narrow and/or re-entrant openings, constrictions withinthe feature, and high aspect ratios. Examples of features that can befilled are depicted in FIGS. 1A-1C. FIG. 1A shows an example of across-sectional depiction of a vertical feature 101 to be filled withtungsten. The feature can include a feature hole 105 in a substrate 103.The substrate may be a silicon wafer, e.g., 200-mm wafer, 300-mm wafer,450-mm wafer, including wafers having one or more layers of materialsuch as dielectric, conducting, or semi-conducting material depositedthereon. In some embodiments, the feature hole 105 may have an aspectratio of at least about 2:1, at least about 4:1, at least about 6:1 orhigher. The feature hole 105 may also have a dimension near the opening,e.g., an opening diameter or line width, of between about 10 nm to 500nm, for example between about 25 nm to 300 nm. The feature hole 105 canbe referred to as an unfilled feature or simply a feature. The feature,and any feature, may be characterized in part by an axis 118 thatextends through the length of the feature, with vertically-orientedfeatures having vertical axes and horizontally-oriented features havinghorizontal axes.

FIG. 1B shows an example of a feature 101 that has a re-entrant profile.A re-entrant profile is a profile that narrows from a bottom, closedend, or interior of the feature to the feature opening. According tovarious embodiments, the profile may narrow gradually and/or include anoverhang at the feature opening. FIG. 1B shows an example of the latter,with an under-layer 113 lining the sidewall or interior surfaces of thefeature hole 105. The under-layer 113 can be for example, a diffusionbarrier layer, an adhesion layer, a nucleation layer, a combination ofthereof, or any other applicable material. The under-layer 113 forms anoverhang 115 such that the under-layer 113 is thicker near the openingof the feature 101 than inside the feature 101.

In some embodiments, features having one or more constrictions withinthe feature may be filled. FIG. 1C shows examples of views of variousfilled features having constrictions. Each of the examples (a), (b) and(c) in FIG. 1C includes a constriction 109 at a midpoint within thefeature. The constriction 109 can be, for example, between about 15nm-20 nm wide. Constrictions can cause pinch off during deposition oftungsten in the feature using conventional techniques, with depositedtungsten blocking further deposition past the constriction before thatportion of the feature is filled, resulting in voids in the feature.Example (b) further includes a liner/barrier overhang 115 at the featureopening. Such an overhang could also be a potential pinch-off point.Example (c) includes a constriction 112 further away from the fieldregion than the overhang 115 in example (b). As described further below,methods described herein allow void-free fill as depicted in FIG. 1C.

Horizontal features, such as in 3-D memory structures, can also befilled. FIG. 1D shows an example of a word line 150 in a VNAND structure148 that includes a constriction 151. In some embodiments, theconstrictions can be due to the presence of pillars in a VNAND or otherstructure. FIG. 1E, for example, shows a plan view of pillars 125 in aVNAND structure, with FIG. 1F showing a simplified schematic of across-sectional depiction of the pillars 125. Arrows in FIG. 1Erepresent deposition material; as pillars 125 are disposed between anarea 127 and a gas inlet or other deposition source, adjacent pillarscan result in constrictions that present challenges in void free fill ofan area 127.

FIG. 1G provides another example of a view horizontal feature, forexample, of a VNAND or other structure including pillar constrictions151. The example in FIG. 1G is open-ended, with material to be depositedable to enter laterally from two sides as indicated by the arrows. (Itshould be noted that example in FIG. 1G can be seen as a 2-D rendering3-D features of the structure, with the FIG. 1G being a cross-sectionaldepiction of an area to be filled and pillar constrictions shown in thefigure representing constrictions that would be seen in a plan ratherthan cross-sectional view.) In some embodiments, 3-D structures can becharacterized with the area to be filled extending along threedimensions (e.g., in the X, Y and Z-directions in the example of FIG.1F), and can present more challenges for fill than filling holes ortrenches that extend along one or two dimensions. For example,controlling fill of a 3-D structure can be challenging as depositiongasses may enter a feature from multiple dimensions.

Filling features with tungsten-containing materials may cause formationof voids and seams inside the filled features. A void is region in thefeature that is left unfilled. A void can form, for example, when thedeposited material forms a pinch point within the feature, sealing offan unfilled space within the feature preventing reactant entry anddeposition.

There are multiple potential causes for void and seam formation. One isan overhang formed near the feature opening during deposition oftungsten-containing materials or, more typically, other materials, suchas a diffusion barrier layer or a nucleation layer. An example is shownin FIG. 1B.

Another cause of void or seam formation that is not illustrated in FIG.1B but that nevertheless may lead to seam formation or enlarging seamsis curved (or bowed) side walls of feature holes, which are alsoreferred to as bowed features. In a bowed feature the cross-sectionaldimension of the cavity near the opening is smaller than that inside thefeature. Effects of these narrower openings in the bowed features aresomewhat similar to the overhang problem described above. Constrictionswithin a feature such as shown in FIGS. 1C, 1D and 1G also presentchallenges for tungsten fill without few or no voids and seams.

Even if void free fill is achieved, tungsten in the feature may containa seam running through the axis or middle of the via, trench, line orother feature. This is because tungsten growth can begin at the sidewalland continues until the grains meet with tungsten growing from theopposite sidewall. This seam can allow for trapping of impuritiesincluding fluorine-containing compounds such as hydrofluoric acid (HF).During chemical mechanical planarization (CMP), coring can alsopropagate from the seam. According to various embodiments, the methodsdescribed herein can reduce or eliminate void and seam formation. Themethods described herein may also address one or more of the following:

1) Very challenging profiles: Void free fill can be achieved in mostre-entrant features using dep-etch-dep cycles as described in U.S.patent application Ser. No. 13/351,970, incorporated by referenceherein. However, depending on the dimensions and geometry, multipledep-etch cycles may be needed to achieve void-free fill. This can affectprocess stability and throughput. Embodiments described herein canprovide feature fill with fewer or no dep-etch-dep cycles.

2) Small features and liner/barrier impact: In cases where the featuresizes are extremely small, tuning the etch process without impacting theintegrity of the underlayer liner/barrier can be very difficult. In somecases intermittent Ti attack—possibly due to formation of a passivatingTiFx layer during the etch—can occur during a W-selective etch.

3) Scattering at W grain boundaries: Presence of multiple W grainsinside the feature can result in electron loss due to grain boundaryscattering. As a result, actual device performance will be degradedcompared to theoretical predictions and blanket wafer results.

4) Reduced via volume for W fill: Especially in smaller and newerfeatures, a significant part of the metal contact is used up by the Wbarrier (TiN, WN etc.). These films are typically higher resistivitythan W and negatively impact electrical characteristics like contactresistance etc.

FIGS. 2-4 provide overviews of various processes of tungsten featurefill that can address the above issues, with examples of tungsten fillof various features described with reference to FIGS. 5-7.

FIG. 2 is a process flow diagram illustrating certain operations in amethod of filling a feature with tungsten. The method begins at a block201 with selective inhibition of a feature. Selective inhibition, whichmay also be referred to as selective passivation, differentialinhibition, or differential passivation, involves inhibiting subsequenttungsten nucleation on a portion of the feature, while not inhibitingnucleation (or inhibiting nucleation to a lesser extent) on theremainder of the feature. For example, in some embodiments, a feature isselectively inhibited at a feature opening, while nucleation inside thefeature is not inhibited. Selective inhibition is described furtherbelow, and can involve, for example, selectively exposing a portion ofthe feature to activated species of a plasma. In certain embodiments,for example, a feature opening is selectively exposed to a plasmagenerated from molecular nitrogen gas. As discussed further below, adesired inhibition profile in a feature can be formed by appropriatelyselecting one or more of inhibition chemistry, substrate bias power,plasma power, process pressure, exposure time, and other processparameters.

Once the feature is selectively inhibited, the method can continue atblock 203 with selective deposition of tungsten according to theinhibition profile. Block 203 may involve one or more chemical vapordeposition (CVD) and/or atomic layer deposition (ALD) processes,including thermal, plasma-enhanced CVD and/or ALD processes. Thedeposition is selective in that the tungsten preferentially grows on thelesser- and non-inhibited portions of the feature. In some embodiments,block 203 involves selectively depositing tungsten in a bottom orinterior portion of the feature until a constriction is reached orpassed.

After selective deposition according to the inhibition profile isperformed, the method can continue at block 205 with filling the rest ofthe feature. In certain embodiments, block 205 involves a CVD process inwhich a tungsten-containing precursor is reduced by hydrogen to deposittungsten. While tungsten hexafluoride (WF₆) is often used, the processmay be performed with other tungsten precursors, including, but notlimited to, tungsten hexachloride (WCl₆), organo-metallic precursors,and precursors that are free of fluorine such as MDNOW(methylcyclopentadienyl-dicarbonylnitrosyl-tungsten) and EDNOW(ethylcyclopentadienyl-dicarbonylnitrosyl-tungsten). In addition, whilehydrogen can be used as the reducing agent in the CVD deposition, otherreducing agents including silane may be used in addition or instead ofhydrogen. In another embodiment, tungsten hexacarbonyl (W(CO)₆) may beused with or without a reducing agent. Unlike with ALD and pulsednucleation layer (PNL) processes described further below, in a CVDtechnique, the WF₆ and H₂ or other reactants are simultaneouslyintroduced into the reaction chamber. This produces a continuouschemical reaction of mix reactant gases that continuously forms tungstenfilm on the substrate surface. Methods of depositing tungsten filmsusing CVD are described in U.S. patent application Ser. Nos. 12/202,126,12/755,248 and 12/755,259, which are incorporated by reference herein intheir entireties for the purposes of describing tungsten depositionprocesses. According to various embodiments, the methods describedherein are not limited to a particular method of filling a feature butmay include any appropriate deposition technique.

In some embodiments, block 205 may involve continuing a CVD depositionprocess started at block 203. Such a CVD process may result indeposition on the inhibited portions of the feature, with nucleationoccurring more slowly than on the non-inhibited portions of the feature.In some embodiments, block 205 may involve deposition of a tungstennucleation layer over at least the inhibited portions of the feature.

According to various embodiments, the feature surface that isselectively inhibited can be a barrier or liner layer, such as a metalnitride layer, or it can be a layer deposited to promote nucleation oftungsten. FIG. 3 shows an example of a method in which a tungstennucleation layer is deposited in the feature prior to selectiveinhibition. The method begins at block 301 with deposition of the thinconformal layer of tungsten in the feature. The layer can facilitatesubsequent deposition of bulk tungsten-containing material thereon. Incertain embodiments, the nucleation layer is deposited using a PNLtechnique. In a PNL technique, pulses of a reducing agent, purge gases,and tungsten-containing precursor can be sequentially injected into andpurged from the reaction chamber. The process is repeated in a cyclicalfashion until the desired thickness is achieved. PNL broadly embodiesany cyclical process of sequentially adding reactants for reaction on asemiconductor substrate, including ALD techniques. PNL techniques fordepositing tungsten nucleation layers are described in U.S. Pat. Nos.6,635,965; 7,589,017; 7,141,494; 7,772,114; 8,058,170 and in U.S. patentapplication Ser. Nos. 12/755,248 and 12/755,259, which are incorporatedby reference herein in their entireties for the purposes of describingtungsten deposition processes. Block 301 is not limited to a particularmethod of tungsten nucleation layer deposition, but includes PNL, ALD,CVD, and physical vapor deposition (PVD) techniques for depositing athin conformal layer. The nucleation layer can be sufficiently thick tofully cover the feature to support high quality bulk deposition;however, because the resistivity of the nucleation layer is higher thanthat of the bulk layer, the thickness of the nucleation layer may beminimized to keep the total resistance as low as possible. Examplethicknesses of films deposited in block 301 can range from less than 10Å to 100 Å. After deposition of the thin conformal layer of tungsten inblock 301, the method can continue with blocks 201, 203, and 205 asdescribed above with reference to FIG. 2. An example of filling afeature according to a method of FIG. 3 is described below withreference to FIG. 5.

FIG. 4 shows an example of a method in which completing filling thefeature (e.g., block 205 in FIG. 2 or 3) can involve repeating selectiveinhibition and deposition operations. The method can begin at block 201,as described above with respect to FIG. 2, in which the feature isselectively inhibited, and continue at block 203 with selectivedeposition according to the inhibition profile. Blocks 201 and 203 arethen repeated one or more times (block 401) to complete feature fill. Anexample of filling a feature according to a method of FIG. 4 isdescribed below with reference to FIG. 6.

Still further, selective inhibition can be used in conjunction withselective deposition. Selective deposition techniques are described inU.S. Provisional Patent Application No. 61/616,377, referenced above.

According to various embodiments, selective inhibition can involveexposure to activated species that passivate the feature surfaces. Forexample, in certain embodiments, a tungsten (W) surface can bepassivated by exposure to a nitrogen-based or hydrogen-based plasma. Insome embodiments, inhibition can involve a chemical reaction betweenactivated species and the feature surface to form a thin layer of acompound material such as tungsten nitride (WN) or tungsten carbide(WC). In some embodiments, inhibition can involve a surface effect suchas adsorption that passivates the surface without forming a layer of acompound material. Activated species may be formed by any appropriatemethod including by plasma generation and/or exposure to ultraviolet(UV) radiation. In some embodiments, the substrate including the featureis exposed to a plasma generated from one or more gases fed into thechamber in which the substrate sits. In some embodiments, one or moregases may be fed into a remote plasma generator, with activated speciesformed in the remote plasma generator fed into a chamber in which thesubstrate sits. The plasma source can be any type of source includingradio frequency (RF) plasma source or microwave source. The plasma canbe inductively and/or capacitively-coupled. Activated species caninclude atomic species, radical species, and ionic species. In certainembodiments, exposure to a remotely-generated plasma includes exposureto radical and atomized species, with substantially no ionic speciespresent in the plasma such that the inhibition process is notion-mediated. In other embodiments, ion species may be present in aremotely-generated plasma. In certain embodiments, exposure to anin-situ plasma involves ion-mediated inhibition. For the purposes ofthis application, activated species are distinguished from recombinedspecies and from the gases initially fed into a plasma generator.

Inhibition chemistries can be tailored to the surface that will besubsequently exposed to deposition gases. For tungsten (W) surfaces, asformed for example in a method described with reference to FIG. 3,exposure to nitrogen-based and/or hydrogen-based plasmas inhibitssubsequent tungsten deposition on the W surfaces. Other chemistries thatmay be used for inhibition of tungsten surfaces include oxygen-basedplasmas and hydrocarbon-based plasmas. For example, molecular oxygen ormethane may be introduced to a plasma generator.

As used herein, a nitrogen-based plasma is a plasma in which the mainnon-inert component is nitrogen. An inert component such as argon,xenon, or krypton may be used as a carrier gas. In some embodiments, noother non-inert components are present in the gas from which the plasmais generated except in trace amounts. In some embodiments, inhibitionchemistries may be nitrogen-containing, hydrogen-containing,oxygen-containing, and/or carbon-containing, with one or more additionalreactive species present in the plasma. For example, U.S. PatentApplication No. 13/016,656, incorporated by reference herein, describespassivation of a tungsten surface by exposure to nitrogen trifluoride(NF₃). Similarly, fluorocarbons such as CF₄ or C₂F₈ may be used.However, in certain embodiments, the inhibition species arefluorine-free to prevent etching during selective inhibition.

In certain embodiments, UV radiation may be used in addition to orinstead of plasma to provide activated species. Gases may be exposed toUV light upstream of and/or inside a reaction chamber in which thesubstrate sits. Moreover, in certain embodiments, non-plasma, non-UV,thermal inhibition processes may be used. In addition to tungstensurfaces, nucleation may be inhibited on liner/barrier layers surfacessuch as TiN and/or WN surfaces. Any chemistry that passivates thesesurfaces may be used. For TiN and WN, this can include exposure tonitrogen-based or nitrogen-containing chemistries. In certainembodiments, the chemistries described above for W may also be employedfor TiN, WN, or other liner layer surfaces.

Tuning an inhibition profile can involve appropriately controlling aninhibition chemistry, substrate bias power, plasma power, processpressure, exposure time, and other process parameters. For in situplasma processes (or other processes in which ionic species arepresent), a bias can be applied to the substrate. Substrate bias can, insome embodiments, significantly affect an inhibition profile, withincreasing bias power resulting in active species deeper within thefeature. For example, 100 W DC bias on a 300 mm substrate may resultinhibition the top half of a 1500 nm deep structure, while a 700 W biasmay result in inhibition of the entire structure. The absolute biaspower appropriate a particular selective inhibition will depend on thesubstrate size, the system, plasma type, and other process parameters,as well as the desired inhibition profile, however, bias power can beused to tune top-to-bottom selectivity, with decreasing bias powerresulting in higher selectivity. For 3-D structures in which selectivityis desired in a lateral direction (tungsten deposition preferred in theinterior of the structure), but not in a vertical direction, increasedbias power can be used to promote top-to-bottom deposition uniformity.

While bias power can be used in certain embodiments as the primary oronly knob to tune an inhibition profile for ionic species, in certainsituations, other performing selective inhibition uses other parametersin addition to or instead of bias power. These include remotelygenerated non-ionic plasma processes and non-plasma processes. Also, inmany systems, a substrate bias can be easily applied to tune selectivityin vertical but not lateral direction. Accordingly, for 3-D structuresin which lateral selectivity is desired, parameters other than bias maybe controlled, as described above.

Inhibition chemistry can also be used to tune an inhibition profile,with different ratios of active inhibiting species used. For example,for inhibition of W surfaces, nitrogen may have a stronger inhibitingeffect than hydrogen; adjusting the ratio of N₂ and H₂ gas in a forminggas-based plasma can be used to tune a profile. The plasma power mayalso be used to tune an inhibition profile, with different ratios ofactive species tuned by plasma power. Process pressure can be used totune a profile, as pressure can cause more recombination (deactivatingactive species) as well as pushing active species further into afeature. Process time may also be used to tune inhibition profiles, withincreasing treatment time causing inhibition deeper into a feature.

In some embodiments, selective inhibition can be achieved by performingoperation 203 in a mass transport limited regime. In this regime, theinhibition rate inside the feature is limited by amounts of and/orrelative compositions of different inhibition material components (e.g.,an initial inhibition species, activated inhibition species, andrecombined inhibition species) that diffuse into the feature. In certainexamples, inhibition rates depend on various components' concentrationsat different locations inside the feature.

Mass transport limiting conditions may be characterized, in part, byoverall inhibition concentration variations. In certain embodiments, aconcentration is less inside the feature than near its opening resultingin a higher inhibition rate near the opening than inside. This in turnleads to selective inhibition near the feature opening. Mass transportlimiting process conditions may be achieved by supplying limited amountsof inhibition species into the processing chamber (e.g., use lowinhibition gas flow rates relative to the cavity profile anddimensions), while maintaining relative high inhibition rates near thefeature opening to consume some activated species as they diffuse intothe feature. In certain embodiment, a concentration gradient issubstantial, which may be caused relatively high inhibition kinetics andrelatively low inhibition supply. In certain embodiments, an inhibitionrate near the opening may also be mass transport limited, though thiscondition is not required to achieve selective inhibition.

In addition to the overall inhibition concentration variations insidefeatures, selective inhibition may be influenced by relativeconcentrations of different inhibition species throughout the feature.These relative concentrations in turn can depend on relative dynamics ofdissociation and recombination processes of the inhibition species. Asdescribed above, an initial inhibition material, such as molecularnitrogen, can be passed through a remote plasma generator and/orsubjected to an in-situ plasma to generate activated species (e.g.,atomic nitrogen, nitrogen ions). However, activated species mayrecombine into less active recombined species (e.g., nitrogen molecules)and/or react with W, WN, TiN, or other feature surfaces along theirdiffusion paths. As such, different parts of the feature may be exposedto different concentrations of different inhibition materials, e.g., aninitial inhibition gas, activated inhibition species, and recombinedinhibition species. This provides additional opportunities forcontrolling selective inhibition. For example, activated species aregenerally more reactive than initial inhibition gases and recombinedinhibition species. Furthermore, in some cases, the activated speciesmay be less sensitive to temperature variations than the recombinedspecies. Therefore, process conditions may be controlled in such a waythat removal is predominantly attributed to activated species. As notedabove, some species may be more reactive than others. Furthermore,specific process conditions may result in activated species beingpresent at higher concentrations near features' openings than inside thefeatures. For example, some activated species may be consumed (e.g.,reacted with feature surface materials and/or adsorbed on the surface)and/or recombined while diffusing deeper into the features, especiallyin small high aspect ratio features. Recombination of activated speciescan also occur outside of features, e.g., in the showerhead or theprocessing chamber, and can depends on chamber pressure. Therefore,chamber pressure may be specifically controlled to adjust concentrationsof activated species at various points of the chamber and features.

Flow rates of the inhibition gas can depend on a size of the chamber,reaction rates, and other parameters. A flow rate can be selected insuch a way that more inhibition material is concentrated near theopening than inside the feature. In certain embodiments, these flowrates cause mass-transport limited selective inhibition. For example, aflow rate for a 195-liter chamber per station may be between about 25sccm and 10,000 sccm or, in more specific embodiments, between about 50sccm and 1,000 sccm. In certain embodiments, the flow rate is less thanabout 2,000 sccm, less than about 1,000 sccm, or more specifically lessthan about 500 sccm. It should be noted that these values are presentedfor one individual station configured for processing a 300-mm substrate.These flow rates can be scaled up or down depending on a substrate size,a number of stations in the apparatus (e.g., quadruple for a fourstation apparatus), a processing chamber volume, and other factors.

In certain embodiments, the substrate can be heated up or cooled downbefore selective inhibition. Various devices may be used to bring thesubstrate to the predetermined temperature, such as a heating or coolingelement in a station (e.g., an electrical resistance heater in stalledin a pedestal or a heat transfer fluid circulated through a pedestal),infrared lamps above the substrate, igniting plasma, etc.

A predetermined temperature for the substrate can be selected to inducea chemical reaction between the feature surface and inhibition speciesand/or promote adsorption of the inhibition species, as well as tocontrol the rate of the reaction or adsorption. For example, atemperature may be selected to have high reaction rate such that moreinhibition occurs near the opening than inside the feature. Furthermore,a temperature may be also selected to control recombination of activatedspecies (e.g., recombination of atomic nitrogen into molecular nitrogen)and/or control which species (e.g., activated or recombined species)contribute predominantly to inhibition. In certain embodiments, asubstrate is maintained at less than about 300° C., or more particularlyat less than about 250° C., or less than about 150° C., or even lessthan about 100° C. In other embodiments, a substrate is heated tobetween about 300° C. and 450° C. or, in more specific embodiments, tobetween about 350° C. and 400° C. Other temperature ranges may be usedfor different types of inhibition chemistries. Exposure time can also beselected to cause selective inhibition. Example exposure times can rangefrom about 10 s to 500 s, depending on desired selectivity and featuredepth.

As described above, aspects of the invention can be used for VNANDwordline (WL) fill. While the below discussion provides a framework forvarious methods, the methods are not so limited and can be implementedin other applications as well, including logic and memory contact fill,DRAM buried wordline fill, vertically integrated memory gate/wordlinefill, and 3D integration (TSV).

FIG. 1F, described above, provides an example of a VNAND wordlinestructure to be filled. As discussed above, feature fill of thesestructures can present several challenges including constrictionspresented by pillar placement. In addition, a high feature density cancause a loading effect such that reactants are used up prior to completefill.

Various methods are described below for void-free fill through theentire WL. In certain embodiments, low resistivity tungsten isdeposited. FIG. 5 shows a sequence in which non-conformal selectiveinhibition is used to fill in the interior of the feature before pinchoff. In FIG. 5, a structure 500 is provided with a liner layer surface502. The liner layer surface 502 may be for example, TiN or WN. Next, aW nucleation layer 504 is conformally deposited on the liner layer 502.A PNL process as described above can be used. Note that in someembodiments, this operation of depositing a conformal nucleation layermay be omitted. Next, the structure is exposed to an inhibitionchemistry to selectively inhibit portions 506 of the structure 500. Inthis example, the portions 508 through the pillar constrictions 151 areselectively inhibited. Inhibition can involve for example, exposure to adirect (in-situ) plasma generated from a gas such as N₂, H₂, forminggas, NH₃, O₂, CH₄, etc. Other methods of exposing the feature toinhibition species are described above. Next, a CVD process is performedto selectively deposit tungsten in accordance with the inhibitionprofile: bulk tungsten 510 is preferentially deposited on thenon-inhibited portions of the nucleation layer 504, such thathard-to-fill regions behind constrictions are filled. The remainder ofthe feature is then filled with bulk tungsten 510. As described abovewith reference to FIG. 2, the same CVD process used to selectivelydeposit tungsten may be used to remainder of the feature, or a differentCVD process using a different chemistry or process conditions and/orperformed after a nucleation layer is deposited may be used.

In some embodiments, methods described herein may be used for tungstenvia fill. FIG. 6 shows an example of a feature hole 105 including aunder-layer 113, which can be, for example, a metal nitride or otherbarrier layer. A tungsten layer 653 is conformally deposited in thefeature hole 10, for example, by a PNL and/or CVD method. (Note thatwhile the tungsten layer 653 is conformally deposited in the featurehole 105 in the example of FIG. 6, in some other embodiments, tungstennucleation on the under-layer 113 can be selectively inhibited prior toselective deposition of the tungsten layer 653.) Further deposition onthe tungsten layer 653 is then selectively inhibited, forming inhibitedportion 655 of the tungsten layer 653 near the feature opening. Tungstenis then selectively deposited by a PNL and/or CVD method in accordancewith the inhibition profile such that tungsten is preferentiallydeposited near the bottom and mid-section of the feature. Depositioncontinues, in some embodiments with one or more selective inhibitioncycles, until the feature is filled. As described above, in someembodiments, the inhibition effect at the feature top can be overcome bya long enough deposition time, while in some embodiments, an additionalnucleation layer deposition or other treatment may be performed tolessen or remove the passivation at the feature opening once depositionthere is desired. Note that in some embodiments, feature fill may stillinclude formation of a seam, such as seam 657 depicted in FIG. 6. Inother embodiments, the feature fill may be void-free and seam-free. Evenif a seam is present, it may be smaller than obtained with aconventionally filled feature, reducing the problem of coring duringCMP. The sequence depicted in the example of FIG. 6 ends post-CMP with arelatively small void present.

In some embodiments, the processes described herein may be usedadvantageously even for features that do not have constrictions orpossible pinch-off points. For example, the processes may be used forbottom-up, rather than conformal, fill of a feature. FIG. 7 depicts asequence in which a feature 700 is filled by a method according tocertain embodiments. A thin conformal layer of tungsten 753 is depositedinitially, followed by selective inhibition to form inhibited portions755, layer 753 at the bottom of the feature not treated. CVD depositionresults in a bulk film 757 deposited on at the bottom of the feature.This is then followed by repeated cycles of selective CVD deposition andselective inhibition until the feature is filled with bulk tungsten 757.Because nucleation on the sidewalls of the feature is inhibited exceptnear the bottom of the feature, fill is bottom-up. In some embodiments,different parameters may be used in successive inhibitions to tune theinhibition profile appropriately as the bottom of the feature growscloser to the feature opening. For example, a bias power and/ortreatment time may be decreased is successive inhibition treatments.

Experimental

3D VNAND features similar to the schematic depiction in FIG. 1F wereexposed to plasmas generated from N₂H₂ gas after deposition of aninitial tungsten seed layer. The substrate was biased with a DC bias,with bias power varied from 100 W to 700 W and exposure time variedbetween 20 s and 200 s. Longer time resulted in deeper and widerinhibition, with higher bias power resulting in deeper inhibition.

Table 1 shows effect of treatment time. All inhibition treatments usedexposure to a direct LFRF 2000 W N₂H₂ plasma with a DC bias of 100 W onthe substrate.

TABLE 1 Effect of treatment time on inhibition profile InitialInhibition Tungsten Treatment Subsequent Layer Time Deposition SelectiveDeposition A Nucleation + None 400 s CVD at Non-selective 30 s CVD at300° C. deposition 300° C. B same as A 60 s same as A Non-selectivedeposition C same as A 90 s same as A Yes - deposition only from bottomof feature to slightly less than vertical midpoint. Lateral deposition(wider) at bottom of feature. D same as A 140 s  same as A No deposition

While varying treatment time resulted in vertical and lateral tuning ofinhibition profile as described in Table 1 (split C), varying bias powercorrelated higher to vertical tuning of inhibition profile, with lateralvariation a secondary effect.

As described above, the inhibition effect may be overcome by certain CVDconditions, including longer CVD time and/or higher temperatures, moreaggressive chemistry, etc. Table 2 below, shows the effect of CVD timeon selective deposition.

TABLE 2 Effect of CVD time on selective deposition Subsequent InitialCVD Tungsten Inhibition Deposition Layer Treatment Time (300° C.)Selective Deposition E Nucleation + H₂N₂ 2000 0 no deposition 30 s CVDat W RF direct 300° C. plasma, 90 s, 100 W DC bias F same as E same as E200 s Yes - small amount of deposition extending about 1/6 height offeature from bottom G same as E same as E 400 s Yes - deposition onlyfrom bottom of feature to slightly less than vertical midpoint. Lateraldeposition wider at bottom of feature. H same as E same as E 700 s Yes -deposition through full height of feature, with lateral deposition widerat bottom of feature

Apparatus

Any suitable chamber may be used to implement this novel method.Examples of deposition apparatuses include various systems, e.g., ALTUSand ALTUS Max, available from Novellus Systems, Inc. of San Jose,Calif., or any of a variety of other commercially available processingsystems.

FIG. 8 illustrates a schematic representation of an apparatus 800 forprocessing a partially fabricated semiconductor substrate in accordancewith certain embodiments. The apparatus 800 includes a chamber 818 witha pedestal 820, a shower head 814, and an in-situ plasma generator 816.The apparatus 800 also includes a system controller 822 to receive inputand/or supply control signals to various devices.

In certain embodiments, a inhibition gas and, if present, inert gases,such as argon, helium and others, can be supplied to the remote plasmagenerator 806 from a source 802, which may be a storage tank. Anysuitable remote plasma generator may be used for activating the etchantbefore introducing it into the chamber 818. For example, a Remote PlasmaCleaning (RPC) units, such as ASTRON® i Type AX7670, ASTRON® e TypeAX7680, ASTRON® ex Type AX7685, ASTRON® hf-s Type AX7645, all availablefrom MKS Instruments of Andover, Mass., may be used. An RPC unit istypically a self-contained device generating weakly ionized plasma usingthe supplied etchant. Imbedded into the RPC unit a high power RFgenerator provides energy to the electrons in the plasma. This energy isthen transferred to the neutral inhibition gas molecules leading totemperature in the order of 2000K causing thermal dissociation of thesemolecules. An RPC unit may dissociate more than 60% of incomingmolecules because of its high RF energy and special channel geometrycausing the gas to adsorb most of this energy.

In certain embodiments, an inhibition gas is flown from the remoteplasma generator 806 through a connecting line 808 into the chamber 818,where the mixture is distributed through the shower head 814. In otherembodiments, an inhibition gas is flown into the chamber 818 directlycompletely bypassing the remote plasma generator 806 (e.g., the system800 does not include such generator). Alternatively, the remote plasmagenerator 806 may be turned off while flowing the inhibition gas intothe chamber 818, for example, because activation of the inhibition gasis not needed or will be supplied by an in situ plasma generator.

The shower head 814 or the pedestal 820 typically may have an internalplasma generator 816 attached to it. In one example, the generator 816is a High Frequency (HF) generator capable of providing between about 0W and 10,000 W at frequencies between about 1 MHz and 100 MHz. Inanother example, the generator 816 is a Low Frequency (LF) generatorcapable of providing between about 0 W and 10,000 W at frequencies aslow as about 100 KHz. In a more specific embodiment, a HF generator maydeliver between about 0 W to 5,000 W at about 13.56 MHz. The RFgenerator 816 may generate in-situ plasma to active inhibition species.In certain embodiments, the RF generator 816 can be used with the remoteplasma generator 806 or not used. In certain embodiments, no plasmagenerator is used during deposition.

The chamber 818 may include a sensor 824 for sensing various processparameters, such as degree of deposition, concentrations, pressure,temperature, and others. The sensor 824 may provide information onchamber conditions during the process to the system controller 822.Examples of the sensor 824 include mass flow controllers, pressuresensors, thermocouples, and others. The sensor 824 may also include aninfra-red detector or optical detector to monitor presence of gases inthe chamber and control measures.

Deposition and selective inhibition operations can generate variousvolatile species that are evacuated from the chamber 818. Moreover,processing is performed at certain predetermined pressure levels thechamber 818. Both of these functions are achieved using a vacuum outlet826, which may be a vacuum pump.

In certain embodiments, a system controller 822 is employed to controlprocess parameters. The system controller 822 typically includes one ormore memory devices and one or more processors. The processor mayinclude a CPU or computer, analog and/or digital input/outputconnections, stepper motor controller boards, etc. Typically there willbe a user interface associated with system controller 822. The userinterface may include a display screen, graphical software displays ofthe apparatus and/or process conditions, and user input devices such aspointing devices, keyboards, touch screens, microphones, etc.

In certain embodiments, the system controller 822 controls the substratetemperature, inhibition gas flow rate, power output of the remote plasmagenerator 806 and/or in situ plasma generator 816, pressure inside thechamber 818 and other process parameters. The system controller 822executes system control software including sets of instructions forcontrolling the timing, mixture of gases, chamber pressure, chambertemperature, and other parameters of a particular process. Othercomputer programs stored on memory devices associated with thecontroller may be employed in some embodiments.

The computer program code for controlling the processes in a processsequence can be written in any conventional computer readableprogramming language: for example, assembly language, C, C++, Pascal,Fortran or others. Compiled object code or script is executed by theprocessor to perform the tasks identified in the program. The systemsoftware may be designed or configured in many different ways. Forexample, various chamber component subroutines or control objects may bewritten to control operation of the chamber components necessary tocarry out the described processes. Examples of programs or sections ofprograms for this purpose include process gas control code, pressurecontrol code, and plasma control code.

The controller parameters relate to process conditions such as, forexample, timing of each operation, pressure inside the chamber,substrate temperature, inhibition gas flow rates, etc. These parametersare provided to the user in the form of a recipe, and may be enteredutilizing the user interface. Signals for monitoring the process may beprovided by analog and/or digital input connections of the systemcontroller 822. The signals for controlling the process are output onthe analog and digital output connections of the apparatus 800.

Multi-Station Apparatus

FIG. 9A shows an example of a multi-station apparatus 900. The apparatus900 includes a process chamber 901 and one or more cassettes 903 (e.g.,Front Opening Unified Pods) for holding substrates to be processed andsubstrates that have completed processing. The chamber 901 may have anumber of stations, for example, two stations, three stations, fourstations, five stations, six stations, seven stations, eight stations,ten stations, or any other number of stations. The number of stations inusually determined by a complexity of the processing operations and anumber of these operations that can be performed in a sharedenvironment. FIG. 9A illustrates the process chamber 901 that includessix stations, labeled 911 through 916. All stations in the multi-stationapparatus 900 with a single process chamber 903 are exposed to the samepressure environment. However, each station may have a designatedreactant distribution system and local plasma and heating conditionsachieved by a dedicated plasma generator and pedestal, such as the onesillustrated in FIG. 8.

A substrate to be processed is loaded from one of the cassettes 903through a load-lock 905 into the station 911. An external robot 907 maybe used to transfer the substrate from the cassette 903 and into theload-lock 905. In the depicted embodiment, there are two separate loadlocks 905. These are typically equipped with substrate transferringdevices to move substrates from the load-lock 905 (once the pressure isequilibrated to a level corresponding to the internal environment of theprocess chamber 903) into the station 911 and from the station 916 backinto the load-lock 905 for removal from the processing chamber 903. Amechanism 909 is used to transfer substrates among the processingstations 911-916 and support some of the substrates during the processas described below.

In certain embodiments, one or more stations may be reserved for heatingthe substrate. Such stations may have a heating lamp (not shown)positioned above the substrate and/or a heating pedestal supporting thesubstrate similar to one illustrated in FIG. 8. For example, a station911 may receive a substrate from a load-lock and be used to pre-heat thesubstrate before being further processed. Other stations may be used forfilling high aspect ratio features including deposition and selectiveinhibition operations.

After the substrate is heated or otherwise processed at the station 911,the substrate is moved successively to the processing stations 912, 913,914, 915, and 916, which may or may not be arranged sequentially. Themulti-station apparatus 900 can be configured such that all stations areexposed to the same pressure environment. In so doing, the substratesare transferred from the station 911 to other stations in the chamber901 without a need for transfer ports, such as load-locks.

In certain embodiments, one or more stations may be used to fillfeatures with tungsten-containing materials. For example, stations 912may be used for an initial deposition operation, station 913 may be usedfor a corresponding selective inhibition operation. In the embodimentswhere a deposition-inhibition cycle is repeated, stations 914 may beused for another deposition operations and station 915 may be used foranother inhibition operation. Section 916 may be used for the finalfilling operation. It should be understood that any configurations ofstation designations to specific processes (heating, filling, andremoval) may be used. In some implementations, any of the stations canbe dedicated to one or more of PNL (or ALD) deposition, selectiveinhibition, and CVD deposition.

As an alternative to the multi-station apparatus described above, themethod may be implemented in a single substrate chamber or amulti-station chamber processing a substrate(s) in a single processingstation in batch mode (i.e., non-sequential). In this aspect of theinvention, the substrate is loaded into the chamber and positioned onthe pedestal of the single processing station (whether it is anapparatus having only one processing station or an apparatus havingmulti-stations running in batch mode). The substrate may be then heatedand the deposition operation may be conducted. The process conditions inthe chamber may be then adjusted and the selective inhibition of thedeposited layer is then performed. The process may continue with one ormore deposition-inhibition cycles (if performed) and with the finalfilling operation all performed on the same station. Alternatively, asingle station apparatus may be first used to perform only one of theoperation in the new method (e.g., depositing, selective inhibition,final filling) on multiple substrates after which the substrates may bereturned back to the same station or moved to a different station (e.g.,of a different apparatus) to perform one or more of the remainingoperations.

Multi-Chamber Apparatus

FIG. 9B is a schematic illustration of a multi-chamber apparatus 920that may be used in accordance with certain embodiments. As shown, theapparatus 920 has three separate chambers 921, 923, and 925. Each ofthese chambers is illustrated with two pedestals. It should beunderstood that an apparatus may have any number of chambers (e.g., one,two, three, four, five, six, etc.) and each chamber may have any numberof chambers (e.g., one, two, three, four, five, six, etc.). Each chamber921-525 has its own pressure environment, which is not shared betweenchambers. Each chamber may have one or more corresponding transfer ports(e.g., load-locks). The apparatus may also have a shared substratehandling robot 927 for transferring substrates between the transferports one or more cassettes 929.

As noted above, separate chambers may be used for depositing tungstencontaining materials and selective inhibition of these depositedmaterials in later operations. Separating these two operations intodifferent chambers can help to substantially improve processing speedsby maintaining the same environmental conditions in each chamber. Achamber does not need to change its environment from conditions used fordeposition to conditions used for selective inhibition and back, whichmay involve different chemistries, different temperatures, pressures,and other process parameters. In certain embodiments, it is faster totransfer partially manufactured semiconductor substrates between two ormore different chambers than changing environmental conditions of thesechambers.

Patterning Method/Apparatus:

The apparatus/process described hereinabove may be used in conjunctionwith lithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallycomprises some or all of the following steps, each step enabled with anumber of possible tools: (1) application of photoresist on a workpiece,i.e., substrate, using a spin-on or spray-on tool; (2) curing ofphotoresist using a hot plate or furnace or UV curing tool; (3) exposingthe photoresist to visible or UV or x-ray light with a tool such as awafer stepper; (4) developing the resist so as to selectively removeresist and thereby pattern it using a tool such as a wet bench; (5)transferring the resist pattern into an underlying film or workpiece byusing a dry or plasma-assisted etching tool; and (6) removing the resistusing a tool such as an RF or microwave plasma resist stripper.

1.-20. (canceled)
 21. A method comprising: providing a substrateincluding a structure having one or more laterally-oriented features tobe filled with a tungsten-containing material, the one or morelaterally-oriented features having feature openings and interior regionsaccessible through the feature openings; and inhibiting tungstennucleation in the one or more laterally-oriented features such thattungsten nucleation is inhibited more at the feature openings than atthe interior regions.
 22. The method of claim 21, further comprisingdepositing the tungsten-containing material in the one or morelaterally-oriented features.
 23. The method of claim 21, wherein thestructure comprises a partially fabricated three-dimensional (3-D) NANDstructure and the one or more laterally-oriented features comprisestungsten wordline features.
 24. The method of claim 21, whereininhibiting tungsten nucleation in the one or more laterally-orientedfeatures comprises exposing the structure to a direct plasma.
 25. Themethod of claim 21, wherein inhibiting tungsten nucleation in the one ormore laterally-oriented features comprises exposing the structure to aremotely-generated plasma.
 26. The The method of claim 21, whereininhibiting tungsten nucleation in the one or more laterally-orientedfeatures comprises exposing the structure to a plasma while applying abias voltage to the substrate.
 27. The method of claim 21, whereininhibiting tungsten in the one or more laterally-oriented featurescomprises exposing the structure to one or more of activated species ofnitrogen, hydrogen, oxygen, or carbon.
 28. The method of claim 21,further comprising depositing a tungsten-containing layer in the one ormore laterally-oriented features prior to inhibition.
 29. The method ofclaim 21, wherein inhibiting tungsten nucleation comprises treating atungsten-containing surface of the one or more laterally-orientedfeatures.
 30. The method of claim 21, wherein inhibiting tungstennucleation comprises treating a metal nitride surface of the one or morelaterally-oriented features.
 31. The method of claim 21, whereininhibiting tungsten nucleation in the one or more laterally-orientedfeatures comprises passivating a feature surface without forming acompound material.
 32. The method of claim 21, wherein selectivelyinhibiting tungsten nucleation in the one or more laterally-orientedfeatures comprises forming a tungsten compound material.
 33. The methodof claim 21, wherein inhibiting tungsten nucleation comprises exposingthe one or more laterally-oriented features to nitrogen species.
 34. Themethod of claim 21, wherein inhibiting tungsten nucleation comprisesexposing the one or more laterally-oriented features to hydrogenspecies.
 35. A method comprising: providing a substrate including afeature having one or more feature openings and a feature interior; andexposing the feature to a non-ionic remotely-generated plasma toselectively inhibit tungsten nucleation in the feature such that thereis a differential inhibition profile along a feature axis.
 36. Themethod of claim 35, further comprising selectively depositing tungstenin the feature in accordance with the differential inhibition profile.37. The method of claim 35, wherein the feature is a laterally-orientedfeature having at least openings and the feature axis islaterally-oriented.
 38. The method of claim 37, wherein the feature is awordline feature in a 3-D NAND structure.
 39. An apparatus comprising:one or more chambers configured to support a substrate; an in situplasma generator configured to generate a plasma in one or more of thechambers or a remote plasma generator configured to generate a remoteplasma; gas inlets configured to direct gas or plasma into each of theone or more chambers; and a controller comprising program instructionsfor: generating a nitrogen-based plasma to the substrate such that thesubstrate is exposed to the plasma; after exposing the substrate to theplasma, inletting a tungsten-containing precursor and a reducing agentto a chamber in which the substrate sits to deposit tungsten.